In this specification, where a document, act or item of knowledge is referred to or discussed, this reference or discussion is not an admission that the document, act or item of knowledge or any combination thereof was at the priority date:                part of common general knowledge; or        known to be relevant to an attempt to solve any problem with which this specification is concerned.        
Based upon figures from both the Australian Bureau of Statistics and the US Census Bureau, an estimated 3% of the total population are wheelchair users. Of that number, approximately half are people who use, or have the capacity to use, manual wheelchairs. That percentage is a good indication of the percentage of manual wheelchair users in developed countries of the world.
It is evident that, with the increasing average age of the population and the general advances in medical science that have prolonged the average lifespan, the general population is rapidly growing older. This is likely to lead to an increase in the demand for wheelchairs and mobility aid products. Also, those members of the population who are confined to wheelchairs will demand more user-friendly or comfortable wheelchairs.
Typically, standard wheelchair wheels have a construction based on a wheel rim, hand rim spaced apart from the wheel rim and a plurality of joining pieces attaching the hand rim to the wheel rim. In order to propel the wheelchair, the wheelchair user grips the hand rim and applies sufficient force to propel the wheelchair in the desired direction.
Although effective, the bio-mechanical forces required to propel a wheelchair can lead to secondary injuries, such as carpal tunnel syndrome (CTS), which are commonly diagnosed in wheelchair users.
The incidence of secondary injuries is often attributed to overuse of the arms, wrist and/or fingers during wheelchair activities. In some instances, researchers believe that these secondary injuries are due to the inefficient transmission of power from the hand to the hand rim. Unfortunately, the configuration of a standard wheelchair wheel includes a hand rim having insufficient area to allow for a complete grip between the wheelchair user's palm and fingers. This creates a number of problems. Firstly, there is a reduced contact area between the palm of the hand and the hand rim. The palm, being the strongest and most resilient part of the hand is unable to transfer its full force on the hand rail. The reduced contact area also increases the pressure on localised contact points on the palm of the hand, and results in relatively large forces being transmitted to various delicate nerve points of the hand. Secondly, the inability to grip the hand rim with a larger area of the palm and fingers reduces the body's mechanical efficiency by recruiting muscles for stabilisation on the hand instead of delivering power to the wheelchair.
It is also known that, with conventional wheelchair wheel configurations, there is a risk that fingers of the wheelchair user's hands may be caught or jammed in the area between the wheel and the push rim. That in turn can cause trauma to the hand and fingers—especially when the wheelchair is in motion. Furthermore, the wheelchair user may need to stop the wheelchair quickly, in which instance the force of curtailing the forward momentum of the wheelchair is likely to fall onto the fingers or small areas of the palms of the hands. This in turn may result in trauma to the hands and fingers, including dislocation of the fingers, and abrasion or “friction burns” of the skin.
These problems are even more prevalent in the rehabilitation sector which often needs to introduce people to wheelchairs for the first time. These inexperienced wheelchair users have a higher tendency to damage their hands and fingers when trying to master the use of a wheelchair.
Furthermore, it is not uncommon for an object, such as a stick or part of an item of clothing, to become caught in the space between the hand rim and the wheel. That object can and often does lead to damage to a hand when the user attempts to grip the hand rim and instead catches the moving object. Items of clothing caught in this matter can also be damaged.
One alternative is to use self-propelled or motorised wheelchairs. However, these are significantly more costly to purchase and to maintain. In any event, the users often prefer to be as self sufficient as possible and, in many instances, prefer the physical aspect of the manual wheelchair rather than relying on an electric battery and machine.
The abovementioned problems of trauma to the fingers and hands can be partially alleviated by the wearing of gloves. However, many wheelchair users find gloves uncomfortable (especially in hot weather), not aesthetically pleasing and prone to wearing out quickly.
Furthermore, standard wheelchair wheels are somewhat difficult and expensive to manufacture as a number of parts need to be joined together (eg by welding, screwing or bolting). It is also quite common for the hand rim to become partially detached from the wheel through a breakage along one or more of the joining pieces. It is also common for standard wheelchair wheels to buckle or flex due to structural weaknesses.